This chapter is from the book

This chapter is from the book

This chapter provides an introduction to the MySQL relational database
management system (RDBMS), and to the Structured Query Language (SQL) that
MySQL understands. It lays out basic terms and concepts you should understand,
describes the sampdb sample database that we'll use for examples,
and serves as a tutorial that shows you how to use MySQL to create a database
and interact with it.

Begin here if you are new to databases and perhaps uncertain whether you need
one or can use one. You should also read the chapter if you don't know
anything about MySQL or SQL and need an introductory guide to get started.
Readers who have experience with MySQL or with database systems might want
to skim through the material. However, everybody should read the section "A
Sample Database," to become familiar with the purpose and contents of
the sampdb database that is used throughout the book.

How MySQL Can Help You

This section describes situations in which the MySQL database system is
useful. This will give you an idea of the kinds of things MySQL can do and the
ways in which it can help you. If you don't need to be convinced about the
usefulness of a database systemperhaps because you've already got a
problem in mind and just want to find out how to put MySQL to work helping you
solve ityou can proceed to "A Sample Database."

A database system is essentially a high-powered way to manage lists of
information. The information can come from a variety of sources. It might be
research data, business records, customer requests, sports statistics, sales
reports, personal hobby information, personnel records, bug reports, or student
grades. However, although database systems can deal with a wide range of
information, you don't use such a system for its own sake. If a job is easy
to do already, there's no reason to drag a database into it just to use
one. A grocery list is a good example: You write down the items to get, cross
them off as you do your shopping, and then throw the list away. It's highly
unlikely that you'd use a database for this. Even if you have a palmtop
computer, you'd probably keep track of a grocery list using its notepad
function rather than its database capabilities.

The power of a database system comes into play when the information you want
to organize and manage becomes so voluminous or complex that your records become
more burdensome than you care to deal with by hand. Clearly this is the case for
large corporations processing millions of transactions a day; a database is a
necessity under such circumstances. But even small-scale operations involving a
single person maintaining information of personal interest might require a
database. It's not difficult to think of scenarios in which a database can
be beneficial, because you needn't have huge amounts of information before
that information becomes difficult to manage. Consider the following
situations:

Your carpentry business has several employees. You need to maintain
employee and payroll records so that you know who you've paid and when, and
you must summarize those records so that you can report earnings statements to
the government for tax purposes. You also need to keep track of the jobs your
company has been hired to do and which employees you've scheduled to work
on each job.

You run a network of automobile parts warehouses and need to be able to
tell which ones have any given part in their inventory so that you can fill
customer orders.

That pile of research data you've been collecting over the course of
many years needs to be analyzed for publication. You want to boil down large
amounts of raw data to generate summary information, and to pull out selected
subsets of observations for more detailed statistical analysis.

You're a teacher who needs to keep track of grades and attendance.
Each time you give a quiz or a test, you record every student's grade.
It's easy enough to write down scores in a gradebook, but using the scores
later is a tedious chore. You'd rather avoid sorting the scores for each
test to determine the grading curve, and you'd really rather not add up
each student's scores when you determine final grades at the end of the
grading period. Counting each student's absences is no fun,
either.

The organization for which you serve as the secretary maintains a
directory of members. (The organization could be anythinga professional
society, a club, a repertory company, a symphony orchestra, or an athletic
booster club.) You generate the directory in printed form each year for the
members, based on a word processor document that you edit as membership
information changes. You're tired of maintaining the directory that way
because it limits what you can do with it. It's difficult to sort the
entries in different ways, and you can't easily select just certain parts
of each entry (such as a list consisting only of names and phone numbers). Nor
can you easily find a subset of members, such as those who need to renew their
memberships soonif you could, it would eliminate the job of looking
through the entries each month to find those members who need to be sent renewal
notices. Also, you'd really like to avoid doing all the directory editing
yourself, but the society doesn't have much of a budget, and hiring someone
is out of the question. You've heard about the "paperless office"
that's supposed to result from electronic record-keeping, but you
haven't seen any benefit from it. The membership records are electronic,
but, ironically, aren't in a form that can be used easily for anything
except generating paper by printing the directory!

These scenarios range from situations involving small amounts to large
amounts of information. Their common characteristic is that they involve tasks
that can be performed manually but that could be performed more efficiently by a
database system.

What specific benefits should you expect to see from using a database system
such as MySQL? It depends on your particular needs and requirements, and as
illustrated by the preceding examples, those can vary quite a bit. Let's
look at a type of situation that occurs frequently and is fairly representative
of database use. Database management systems are often employed to handle tasks
such as those for which people use filing cabinets. Indeed, a database is like
a big filing cabinet in some ways, but one with a sophisticated built-in filing
system. There are some important advantages of electronically maintained records
over records maintained by hand. For example, if you work in a dentist's
office setting in which client records are maintained, here are some of the
ways MySQL can help you in its filing system capacity:

Reduced record filing time. You don't have to look through
drawers in cabinets to figure out where to add a new record. You just hand
it to the filing system and let it put the record in the right place for
you.

Reduced record retrieval time. When you're looking for records,
you don't search through each one yourself to find the ones containing
the information you want. If you want to send out reminders to all patients
who haven't been in for their checkup in a while, you ask the filing
system to find the appropriate records for you. Of course, you do this
differently than if you were talking to another person, with whom you'd
say, "Please determine which patients haven't visited within
the last six months." With a database, you invoke a strange incantation:

That can be pretty intimidating if you've never seen anything like
it before, but the prospect of getting results in a second or two rather
than spending an hour shuffling through your records should be attractive.
(In any case, you needn't worry. That odd-looking bit of gobbledygook
won't look strange for long. In fact, you'll understand exactly
what it means by the time you've finished this chapter.)

Flexible retrieval order. You needn't retrieve records according
to the fixed order in which you store them (by patient's last name,
for example). You can tell the filing system to pull out records sorted
in any order you like: by last name, insurance company name, date of last
visit, and so forth.

Flexible output format. After you've found the records in
which you're interested, there's no need to copy the information
manually. You can let the filing system generate a list for you. Sometimes
you might just print the information. Other times you might want to use
it in another program. For example, after you generate the list of patients
who are overdue on their dental visits, you might feed this information
into a word processor that prints out notices that you can send to those
patients. Or you might be interested only in summary information, such
as a count of the selected records. You don't have to count them yourself;
the filing system can generate the summary for you.

Simultaneous multiple-user access to records. With paper records,
if two people want to look up a record at the same time, the second person
must wait for the first one to put the record back. MySQL gives you multiple-user
capability so that both can access the record simultaneously.

Remote access to and electronic transmission of records. Paper
records require you to be where the records are located, or for someone
to make copies and send them to you. Electronic records open up the potential
for remote access to the records or electronic transmission of them. If
your dental group has associates in branch offices, those associates can
access your records from their own locations. You don't need to send
copies by courier. If someone who needs records doesn't have the same
kind of database software you do but does have electronic mail, you can
select the desired records and send their contents electronically.

If you've used database management systems before, you already know about
the benefits just described, and you may be thinking about how to go beyond
the usual "replace the filing cabinet" applications. The manner in
which many organizations use a database in conjunction with a Web site is a
good example. Suppose that your company has an inventory database that is used
by the service desk staff when customers call to find out whether you have
an item in stock and how much it costs. That's a relatively traditional
use for a database. However, if your company puts up a Web site for customers
to visit, you can provide an additional service: a search page that allows
customers to determine item pricing and availability. This gives customers
the information they want, and the way you provide it is by searching the inventory
information stored in your database for the items in questionautomatically.
The customer gets the information immediately, without being put on hold listening
to annoying canned music or being limited by the hours your service desk is
open. And for every customer who uses your Web site, that's one less phone
call that needs to be handled by a person on the service desk payroll. (Perhaps
the Web site can pay for itself this way?)

But you can put the database to even better use than that. Web-based
inventory search requests can provide information not only to your customers,
but to your company as well. The queries tell you what customers are looking
for, and the query results tell you whether you're able to satisfy their
requests. To the extent you don't have what they want, you're probably
losing business. So it makes sense to record information about inventory
searches: what customers were looking for, and whether you had it in stock. Then
you can use this information to adjust your inventory and provide better service
to your customers.

Another Web-based application for databases is to serve up banner
advertisements in Web pages. I don't like them any better than you do, but
the fact remains that they are a popular application for MySQL, which can be
used to store advertisements and retrieve them for display by a Web server. In
addition, MySQL can perform the kind of record-keeping often associated with
this activity by tracking which ads have been served, how many times
they've been displayed, which sites accessed them, and so forth.

So how does MySQL work? The best way to find out is to try it for yourself,
and for that we'll need a database to work with.